Study on the air-lift circulation technique for water-well drilling in karst leaking stratum

This technique is mainly concerned with a new study of water-well drilling method, which is well applied in severe leakage stratum, especially in karst stratum. Unlike other drilling method, air-lift drilling technique applies the compressed air through the dual wall drilling pipe, lifting the air-mud in annular space between the outer pipe and the wall of hole. The accelerated air-mud speeds up the circulating mud to reduce the leakage capacity and lift cuttings rapidly. Several advantages of this drilling technique were found in the fieldwork research which undertook in the 600 m water well drilling in Fangshan, Beijing. The field work research mainly carried out by the experiment of air-lift drilling tools revealed that the broken circulation of drilling mud had been recovered and the flow of the return mud had been largely improved. The drilling speed of this technique is quicker than the air-lift reverse circulation or the mud drilling method. In severe leakage stratum, this technique has been proved to be efficient in solve drilling problems, such as broken circulation and burned drill bit. Further study of air-lift drilling method should be made in relation to other routine water well drilling methods in different karst strata.